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The sight of an omelet sizzling in a pan is a beautiful thing—until the diced onions you carefully folded inside turn blue. Wondering what tainted your meal? You’re not alone. Let’s break down the science behind the unappetizing color change and what to do if it happens in your kitchen.
What's the Difference Between White, Yellow, and Red Onions?
Why Do Red Onions Turn Blue?
Red onions are treasured for their mild flavor, sweetness, and beautiful color. They contain pH-sensitive anthocyanins, a type of flavonoid (natural plant pigment) that gives fruits and vegetables their red, blue, and purple hues. When anthocyanins are exposed to alkaline substances such as egg whites, baking soda, beans, and certain minerals in water or cookware, they can change color from white to blue or blue-green.
The chemical reaction also happens with other types of purple produce, such as red cabbage and cherries. Yellow onions, however, don’t turn blue during the cooking process because they contain a high amount of quercetin (a flavonoid that gives them a yellow hue) instead of anthocyanins. Fun fact: Onion skins contain such vibrant pigments that they can be used to produce natural dyes for Easter eggs, yarns, and fabrics.
Is It Safe to Eat Blue Onions?
Yes, they are completely safe to consume! While encountering blue onions while you’re cooking might make you shudder, the color is due to a natural chemical reaction and won’t impact their flavor or nutritional value. However, if your onions smell musty or feel soft, slimy, or mushy, they’re probably spoiled and ready to toss.
How Do I Fix Blue Onions?
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You can reverse the chemical reaction by adding a splash of acid, such as lemon juice or vinegar. However, this might impact the flavor of what you’re cooking. Avoid cooking red onions (and other purple produce) with alkaline ingredients such as baking soda, which will significantly shift the pH, turning them blue.
Is It Safe to Eat a Boiled Egg With a Green Ring Around the Yolk?
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